With the rapid development of Internet of things and wireless communication technology, embedded devices are widely used in every aspect of our daily lives. Due to the lack of built-in security mechanism, the embedded devices are facing more and more threats from the malicious code attack, DDoS attack and so on. Secure boot technology can assure that the device boots up with an untampered and authorized software provided by a legitimate vendor and becomes a critical step in the device firmware and software security at the booting time. Aiming at designing and implementing the secure booting schemes, researchers have presented many effective approaches. This paper summarizes existing secure boot schemes for embedded devices and also compares and analyses the advantage and disadvantages of these existing schemes.